This invention relates to an internal combustion engine with an auxiliary piston for generating turbulence which is designed to improve the combustibility of the combustible mixture. The auxiliary piston is provided in an auxiliary chamber having a passage communicating with a main combustion chamber so that the forward motion of the auxiliary piston injects a compressed gas through the communicating passage into the main combustion chamber to generate turbulence therein.
Lean combustible mixture systems and exhaust gas recirculation systems are known to be effective in decreasing noxious substances (carbon monoxide, hydrocarbons and especially nitrogen oxides) in automotive exhaust gases. As is also well-known, however, combustible mixtures used in these two systems are composed of partially incombustible compositions, which leads to low flame propagation speed and unstable combustion. As a result, various means have been devised to eliminate such shortcomings and improve combustion. These means include providing a small diameter swirl intake port to generate swirl and thus turbulence in air sucked on the intake stroke, a squish area formed in the combustion chamber to generate turbulence in the combustible mixture, and a torch-ignition type internal combustion engine to cause turbulence in the combustible mixture.
However, these conventional techniques have not been free of drawbacks. In the intake swirl system, the charging efficiency lowers with increasing gas intake, which allows for no further increase in power output. The provision of the squish area in the combustion chamber cannot impart effective trubulence to the combustible mixture before ignition. The torch-ignition internal combustion engine causes turbulence in the early stage of combustion and cannot impart turbulence to the combustible mixture in the latter stage of combustion when it is really needed. In addition, it does not permit control over the timing of turbulence generation. Using a small-diameter intake port together with a large-diameter port also does not allow an ideal adaptation to an engine operating under various conditions such as high speed, high load conditions and idling.
Therefore, an object of this invention is to eliminate the aforementioned shortcomings, namely, to insure an ideal combustibility in the lean mixture combusting system or the voluminous exhaust gas recirculation system by generating sufficient turbulence in the combustible mixture in optimum timing with the stroke of the piston in the main combustion chamber.
This object of the invention is obtained by providing a reciprocating auxiliary piston in an auxiliary chamber having a passage communicating with a main combustion chamber. The auxiliary piston, which is coupled for movement by the main engine shaft, is moved forward at an optimum time as the main piston approaches top dead center on the compression stroke and injects a gas into the main combustion chamber through the communicating passage and, thereby, generates turbulence in the airfuel mixture therein.